Prints made using an ink-jet printer desirably have image resolution of about 6 line pairs/mm, which corresponds to about 84 μm per line or equivalently about 300 dots per inch. They must have a dynamic range of about 128 color density gradations (or levels of gray) or more in order to be comparable in image quality to conventional photographic prints.
Secondary colors are formed as combinations of primary colors. The subtractive primary colors are cyan, magenta and yellow and the secondary ones are red, green and blue. Gray can be produced by equal amounts of cyan magenta and yellow, but less fluid is deposited on the paper if the gray is produced from an ink supply containing only black dye or pigment.
Typically, a print head emits 4 pL droplets. The 4 pL droplet has a diameter of about 20 μm in the air and forms a disk of about 30 μm on the paper. Adjacent droplets are typically aimed to be placed on 21 μm centers so that adjacent disks on the paper have some overlap and thus ensure that full area coverage is obtained and that the misdirection of a jet does not produce visible artifacts. Then, as taught in U.S. Pat. No. 6,089,692 of Anagnostopoulos, if a saturated spot of a secondary color is to be formed, at least 256 droplets (128 of each of the primary colors) have to be deposited per 84×84 μm area. The amount of fluid deposited per unit area is then about 145 mL/m2.
There are a large number of commercial ink-jet papers. Two of the most successful are described briefly here. The first is shown in FIG. 1. The receiver, as described in U.S. Pat. No. 6,045,917 of Missell et al., consists of a plain paper base covered by a polyethylene coat. This coat prevents any fluid, especially water from the ink, from penetrating into the paper base and causing puckering or wrinkling termed “cockle”. The front side of the paper is additionally coated with two layers of polymers containing mordant. The polymer layers absorb the ink by swelling while the dyes are immobilized in the mordant. An anti-curl layer is also coated in the backsides of this paper.
The second commercial paper is described by Kenzo Kasahara, in “A New Quick-Drying, High-Water Resistant Glossy Ink Jet paper,” Proceedings IS&T's NIP 14: 1998 International Conference on Digital printing Technologies, Toronto, Canada, Oct. 18–23, 1998, pp 150–152, and is shown in FIG. 2. Like the first paper, the paper base is coated with a polyethylene film to prevent cockle. The image-receiving layer consists of three separate layers. Each one is made up of ICOS (inorganic core/organic shell) particles in a polyvinyl alcohol binder and boric acid hardener, forming a micro-porous structure. The porosity of all three layers combined is about 25 ml/m2. Each of the ICOS particles, of the order of 0.05 μm in diameter, consists of an anionic silica core surrounded by a cationic polymer shell.
Inkjet print heads have been recently invented that are page wide and have nozzle spacing of finer than 300 per inch. See, for example, U.S. Pat. No. 6,079,821, of Chwalek et al. Such print heads produce 1 to 2 pL droplets which are smaller than the typical droplets produced by the commercial print heads. Also, because they are page wide and have a large number of nozzles, they are capable of ink lay down rates substantially higher than that of the scanning type conventional ink-jet printers.
Significant problems stem from the jetting of dye or pigmented inks onto a media. In many cases a different level of gloss is required so that it is necessary to modify the finish of the media. It is also common that the quality of the image degrades with exposure to ambient air, water, abrasion, and UV components in light. A need therefore exists for a type of image receiver media that is capable of providing a modified finish and/or a protective overcoat layer for the printed image.